It is known to use conventional potentiometers for sensing a vehicle steering angle, where the potentiometer is arranged on two elements that are moving relative to each other during steering. Here, the resistance track of the potentiometer is fixed to one of the two elements, and the wiper of the potentiometer is connected to the other element. The divider voltage is measured between the wiper contact and the reference potential as a measure for the relative positions of the two movable elements. A disadvantage of such potentiometer sensors is that the wiper and the resistance track, on the one hand, must remain in contact with each other, and that on the other hand, they must be maintained movable relative to each other. In addition to the wear of the components, this results also in the problem of sealing. In a humid or dirty environment, the electrical properties of the potentiometer can be influenced negatively, or the contact between the wiper and the resistance track can be broken.
DE 299 23 362 U1, the entire contents of which is incorporated herein by reference, discloses a device for position measurement for an industrial truck where a magnetic position transducer is arranged on a movable axle part of the steering axle. On a second, immobile part of the axle, a sensor arrangement is arranged as a group of offset proximity circuit elements that are integrated in an electrical circuit in such a way that they control an output voltage of the circuit in dependence on the position of the position transducer along the sensor arrangement. The resulting characteristic voltage curve has discrete values, that is, the measurement system acts like a potentiometer with step outputs. The position of the position transducer is indicated in discrete steps according to the distance between two proximity circuit elements, that is, it is indicated only inaccurately.
With only one measurement, the known position measurement devices permit no error recognition in the measurement device. Potentiometers require a physical contact of the elements arranged on the movable components of the steering mechanism, the known magnetic position measurement supplies only discrete measurement values. Inaccurate measurement values are also associated with inaccurate input specifications for an electrical differential, which results in an increased tire wear.
DE 101 60 904 B4, the entire contents of which is incorporated herein by reference, discloses a sensor system for the position measurement on a hydraulic cylinder. A magnet is connected to the piston, and a magnetic sensor is connected to the cylinder.
The objective of the invention is to provide an industrial truck with a contactless and analog position measurement device for steering that enables a simple function check.